Interrelated studies will be carried out with rats to establish more completely both how unsaturated fatty acid metabolism is altered in the diabetic and whether these alterations influence blood platelet aggregation, thus contributing to the more rapid onset of vascular disease in the diabetic. Related studies will be conducted to determine how modification of dietary fat influences both platelet lipid metabolism and platelet aggregation in the diabetic. Experiments will be carried out with cat liver microsomes to verify a report suggesting that the cat is unable to desaturate fatty acids. Dietary fat will be modified to determine how specific defined changes in the fatty acid composition of cat platelet lipids influence platelet aggregation.